1. Field of the Invention
The invention relates to a driving method of a plasma display panel.
2. Description of the Related Arts
At present, a plasma display panel (hereinbelow, abbreviated to PDP) of an AC type (alternating current discharging type) has been manufactured as a thin type display apparatus. In the PDP, two substrates, that is, a front transparent substrate and a rear substrate are arranged so as to face each other through a predetermined gap. A plurality of row electrode pairs extending in the lateral direction of a display screen are formed as pairs on the inner surface of the front transparent substrate (surface which faces the rear substrate) serving as a display plane. Further, a dielectric layer which covers each of the row electrode pairs is formed on the inner surface of the front transparent substrate. A plurality of column electrodes extending in the vertical direction of the display screen are formed on the rear substrate side so as to cross the row electrode pairs. When seen from the display plane side, a discharge cell corresponding to a pixel is formed in a cross portion of the row electrode pair and the column electrode.
To the PDP as mentioned above, a gradation driving using a subfield method is executed so as to obtain a halftone display luminance corresponding to an input video signal.
According to the gradation driving based on the subfield method, a display driving to a video signal of one field is executed in each of a plurality of subfields to each of which the number of times (or period) of light emission to be executed has been allocated. In each subfield, an addressing step and a sustaining step are sequentially executed. In the addressing step, an address discharge is selectively generated between the row electrode and the column electrode in each discharge cell in accordance with an input video signal, thereby forming (or erasing) wall charges of a predetermined amount. In the sustaining step, only the discharge cell in which the wall charges of the predetermined amount have been formed is repetitively discharged and a light-emitting state accompanied by the discharge is maintained. Further, prior to the addressing step, a resetting step is executed in at least the head subfield. In the resetting step, in all discharge cells, a reset discharge is caused between the row electrodes forming the pair, thereby initializing the amount of wall charges remaining in all of the discharge cells.
Since the reset discharge is a relatively strong discharge and does not take part in the contents of an image to be displayed, there is such a problem that the light emission due to the discharge causes a contrast of the image to be deteriorated.
A PDP constructed in such a manner that a magnesium oxide crystal which is excited by irradiation of an electron beam and executes a cathode luminescence light emission having a peak at wavelengths of 200-300 nm is deposited onto the surface of a dielectric layer with which a row electrode pair is covered, thereby shortening a discharge time lag and a driving method of the PDP have, therefore, been disclosed in Japanese Patent Kokai No. 2006-54160. According to the PDP, since a priming effect after the discharge continues for a relatively long time, a weak discharge can be stably caused. By applying a reset pulse having a pulse waveform whose voltage value reaches gradually a peak voltage value with the elapse of time to the row electrodes of the PDP as mentioned above, the weak reset discharge is caused between the adjacent row electrodes. At this time, since a light emission luminance due to the discharge deteriorates by the weakening of the reset discharge, the contrast of the image can be raised.
If the reset discharge is weakened or an execution frequency of the reset discharge is reduced, however, an amount of priming particles which are formed in the discharge cell decreases and such a problem that it is difficult to cause an addressing discharge in the next addressing step occurs.